JP2010507028A - Open-hole nonwoven fabric, and method and apparatus for producing the nonwoven fabric - Google Patents

Abstract

Disclosed is a process for continuous perforation of fabrics that comprise thermoplastic fibers. The process utilizes a combination of heat and pressure to perforate fabrics where the shape. size, and distribution of the individual fabric perforations is define solely by the design of the pattern embossing roll, In particular, the top side of the individual embossing points are not flat but rather have a raised peripheral edge so that the actual fabric contact area of the bond points is much less than total area circumscribed by each bond point. The small ratio of fabric contact area to total bond area concentrates the thermal and compressive forces in the embossing nip and allows a large perforation to be cut out of a fabric moving at high speed through the perforation nip.

Description

  The present invention relates to perforated nonwoven fabrics and methods and apparatus for producing such fabrics.

  For fabrics having a total open area greater than about 10% of the surface of the fabric, it is desirable to produce such fabrics at the standard line speeds of commercial nonwoven production lines. As a result, it becomes possible to manufacture a perforated cloth on the cloth manufacturing line, and it becomes unnecessary to provide another expensive manufacturing process. If the fabric is composed of thermoplastic fibers, the apertures can be formed continuously by applying a combination of heat and pressure to selected points of the fabric.

  Several processes for forming large apertures in thermoplastic fabrics are described in the patent literature. Shimalla describes a two-stage process in US Pat. In this process, a small diameter hole in a thermoplastic fabric is melted by a high-pressure hot embossing calendar, and then the fabric is subjected to a non-recoverable stretch treatment in MD (machine direction) and / or CD (cross direction). To enlarge the hole. Therefore, the melted edge portion of the hole contributes to the improvement of the strength and integrity of the hole cloth.

  Benson describes an alternative two-stage process in US Pat. In this process, another hot embossing step is applied to the point bonded fabric that causes selected points of the fabric to weaken by melting but does not substantially perforate. The selectively weakened fabric is then subjected to an incremental stretching process to first break the weakened points to form narrow holes, and then to the narrow holes. Is stretched, thereby forming large apertures in the fabric.

  Both Patent Documents 1 and 2 have significantly greater non-recoverability to heat-perforated or heat-fragile fabrics to significantly enlarge the initial small apertures or small fragile areas of the pre-stretched fabric. It has a common important feature that it is necessary to perform the stretching process.

  Coslett et al., In US Pat. Nos. 6,037,036 and 5, describe a thermoplastic fabric and thermoplastic fabric / film laminate that are optimal for forming apertures. Here, the embossing point of each perforating roll has a fabric contact area that is substantially the same size as the size of the resulting aperture. This patent suggests that it is advantageous to mix high melting fibers with either low melting fibers or low melting films resulting in clean and well-defined perforations. . Low elongation high strength polypropylene short fibers are preferred over high elongation low strength polypropylene fibers and are superior in forming perforated pores. Gillespie et al. Also identified in US Pat. No. 6,057,637 a fabric fiber composition that has an especially improving effect on thermal perforation by hot embossing and subsequent significant stretching.

US Pat. No. 4,588,630 US Pat. No. 5,916,661 US Pat. No. 5,656,119 US Pat. No. 5,567,501 US Pat. No. 5,830,555 US Pat. No. 6,632,504

  There is a need for a process that can obtain an aperture pattern that is an exact replica in the desired fabric design while perforating the fabric at the production rate of a commercial nonwoven line. The Simara and Benson process requires large strains in the fabric by stretching in the MD and / or CD direction to obtain large apertures. The process of Koslet et al. Can produce large apertures, but clean apertures because the thermal and compressive energy that perforates the fabric will be distributed over the entire area of the resulting aperture. The maximum line speed for producing the can be severely limited.

  In one aspect, the present invention provides a nonwoven fabric by removing selected portions of a nonwoven web and thermoplastic fibers that are joined together at a plurality of joining sites to form a coherent and strong nonwoven web. A nonwoven fabric comprising a plurality of apertures to be formed, wherein the plurality of apertures are configured to have an aperture ratio of at least 10% with respect to the surface area of the fabric. Is provided. Opening debris formed from the removed portion of the nonwoven web may removably adhere to at least some of the openings. The edge of the melted thermoplastic fiber extends along the periphery of the open chip. Moreover, the edge part of the molten thermoplastic fiber may extend along the circumference | surroundings of an opening. Nonwovens can have a variety of structures including carded heat bonded nonwovens, airlaid nonwovens, and spunbond nonwovens composed of continuous filaments of thermoplastic polymers. The aperture will be cut cleanly and the boundary will be clearly defined. The fabric is not subjected to non-recoverable stretching.

  Further, the present invention provides a method for producing a perforated nonwoven fabric, a step of guiding a nonwoven fabric composed of thermoplastic fibers into an embossing station along a predetermined traveling path and passing the embossing station; Contacting the nonwoven with an embossing roll having a predetermined patterned surface and applying a heat and pressure to the nonwoven to form a plurality of closed paths that define selected areas of the surface of the fabric. Along the steps of thermally melting the thermoplastic fibers, wherein openings are to be formed in selected areas, and removing selected areas of the fabric from the rest of the cloth; A method characterized by comprising: The plurality of closed paths in which the fibers are thermally melted form an embossed area, the embossed area occupies 10% or less of the surface area of the fabric, the thermoplastic fibers are not melted, and It is good to surround the area | region of the nonwoven fabric which is not embossed. In some embodiments, the plurality of closed paths in which the fibers are thermally melted have a surface area of 2% to 20% relative to the area enclosed by the closed paths.

  The present invention also relates to an embossing roll for producing a perforated nonwoven fabric. The roll includes a cylindrical body and a plurality of raised embossed portions located at predetermined spaced apart positions extending over the entire cylindrical surface of the cylindrical body, and the raised embossed portion is a closed path along the periphery of the raised embossed portion. And a concave land surrounded by the raised land surface, wherein the raised land surface is 2% to 20% of the area of the portion surrounded by the raised land surface. % Surface area. In some advantageous embodiments, the raised embossed portions are provided on the roll at a density such that the raised land surface and the enclosed concave surface occupy at least 10% of the surface area of the cylindrical surface.

  While the invention has been described in general terms, further aspects of the invention will become apparent from the following detailed description and the accompanying drawings.

It is a figure which shows one Embodiment of the joining pattern design for embossing rolls. It is a top view of a roll. FIG. 3 is a schematic diagram of a thermal drilling process. 1 is a schematic diagram of an ultrasonic drilling process. FIG. It is an enlarged photograph of the pierced cloth which shows the opening from which the opening waste is removed, and the opening from which the opening waste is not removed. FIG. 6 is an enlarged view of a single aperture showing open debris loosely held by fibers remaining along the periphery of the embossed area.

  The present invention disclosed herein includes: 1) an embossed pattern design in which individual joint points are recessed such that only the outer peripheral edge of each joint point is in contact with the cloth to be opened at the nip; and 2) the cloth. It is characterized by a post-embossing step that is used to remove the portion of the fabric remaining inside the embossing line from the opening of the fabric at each joint point without any non-recoverable stretching treatment.

  FIG. 1 shows one embodiment of such a joint pattern design (A) in which a raised annular peripheral edge (B) surrounds a central recessed area or a central void area (C). FIG. 2 shows the arrangement of the joining points (A) on the embossed calender roll (D) with a pattern. In this embodiment, the cumulative surface area of the portion occupied by the elliptical joint is about 35% of the surface area of the embossing roll, and the cumulative surface area of the raised annular edge at each joint is the embossing roll surface area. About 5% of the surface area. Thus, the drilling energy in the nip will be concentrated only in a portion of about 5% of the fabric surface area that passes through the nip. The present invention is not limited to any particular shape of the junction points or arrangement of the junction points on any particular embossing roll. In general, the design of a joint point will be appropriate if the contact area of the fabric at the joint point is in the range of 2% to 20% of the area surrounded by the entire joint point. The size, shape, and number of junctions per unit area will vary according to the specific application requirements. The inventors believe that this continuous fabric perforation is most beneficial in applications where the desired open area of the fabric is greater than 10% relative to the surface of the fabric.

  The local heating of the cloth contact point can be performed either by heat conduction from a heated calendar roll or by high frequency vibration of an ultrasonic horn.

  The junction shown in FIG. 1 is designed to ablate the fabric contact points, leaving the fabric chad that will fall out of the aperture. The inventors are surprised by the fact that with appropriate raw material selection and proper embossing nip setting, the perforated debris is held very loosely in the perforations as the embossed textured fabric exits the nip. To find out what should be done. This allows opening debris to be easily removed from these openings by a simple air jet (FIGS. 3a and 3b) as the fabric moves out of the nip. This debris removal action of air injection may be assisted or replaced by the action of a series of brush rolls on the surface of the embossed textured fabric.

  Such a cloth behavior is more preferable than the cloth behavior in which the hole scraps are completely removed at the nip. This is because debris does not block the recessed cavity of the embossing roll, and the debris removal station can be moved away from the vicinity of the nip, thereby facilitating collection of debris for reuse. Because. It is important to note that no non-recoverable stretch treatment of the type described in the Shimara and Benson patents is required to remove the non-porous debris.

  FIG. 4 shows a magnified view of the embossed fabric with some of the open debris removed and some of the open debris remaining in place. FIG. 5 shows an enlarged view of perforated debris that is partially held in place by some of the uncut fibers of the nonwoven. The fabric shown in FIGS. 4 and 5 is embossed with the pattern described in FIGS. 1 and 2.

  This fabric punching process has several advantages over the prior art. In a suitable fabric, large (eg, greater than 10%) open areas can be formed at high speed without any non-recoverable stretch treatment in any direction. The non-recoverable stretch treatment of the fabric can degrade material properties. The shape and distribution of the individual apertures is precisely defined and will not be unpredictably distorted by subsequent web stretching. Accordingly, these openings can define various patterns in the nonwoven fabric. The energy for obtaining the apertures is concentrated only in the locations necessary to excise the large apertures. Thereby, it is possible to perform at the maximum line speed at which good web drilling can be performed.

[Example 1]
With an embossing roll with raised embossing configured to provide a land area of about 5% of the area of the embossing roll, an 18 g / m ² spunbond polyethylene spunbond nonwoven is produced at a line speed of 305 m / min. Hot embossed.

[Example 2]
The embossing rolls shown in FIGS. 1 and 2 were designed such that an annular raised land surface having a fabric contact area of 5% or less produces an open area of at least 20% of the fabric area.

This embossing roll was used while being placed opposite to a flat anvil roll in a calendar stand. The nip pressure was set to 1250 psi (8.6184 MPa (1 psi = 6895 Pa)). The patterned embossing roll was heated to 254 ° C and the anvil roll was heated to 256 ° C. Operating at a line speed of 100 ft / min (30.48 m / min (1 ft = 0.3048 m)) and using this calendar, a sheath-core bicomponent construction with a 50% polyethylene sheath and a 50% polypropylene core. A 28.1 g / m ² spunbond nonwoven formed from continuous filaments was hot embossed. By directing a high velocity air flow into the fabric, the debris can be easily blown out of the fabric, resulting in a clean and well-defined perforation without any fabric cracking or distortion. It was. This perforated cloth was kept in a soft state.

[Example 3]
The embossing procedure of Example 2 was carried out using a spunbonded nonwoven fabric in which the filament had a segmented pie-like cross-sectional structure consisting of 6 segments of alternating polypropylene and polyethylene. . Openings similar to those of Example 2 were observed.

[Example 4]
A 18 g / m ² spunbond polypropylene nonwoven fabric was hot embossed using the same embossing procedure as in Example 2 except that the roll temperature was increased.

[Example 5]
The embossing procedure of Example 2 was performed on a 24.1 g / m ² spunbond-meltblown-spunbond composite nonwoven laminate. Opening debris could be easily removed by air and / or rubbing. Openings with clean and clear boundaries were observed and the fabric was kept soft.

Claims (19)

Thermoplastic fibers forming a strong non-woven web joined together at a plurality of joining sites and a plurality of apertures formed by removing selected portions of the non-woven web Configured,
A nonwoven fabric in which the plurality of apertures are configured to have an aperture ratio of at least 10% with respect to the surface area of the nonwoven fabric.   The non-woven fabric according to claim 1, wherein the non-woven fabric is formed from a removed portion of the non-woven web and has debris that removably adheres to at least some of the perforations.   The nonwoven fabric of Claim 2 which has the edge part of the thermoplastic fiber extended along the circumference | surroundings of the said hole waste, and fuse | melted.   The nonwoven fabric according to claim 1, wherein the nonwoven fabric has a peripheral edge portion of a thermoplastic fiber that extends and melts along the periphery of the opening.   The carded heat-bonded nonwoven fabric composed of thermoplastic short fibers, the air-laid nonwoven fabric composed of thermoplastic short fibers, and the spunbond nonwoven fabric composed of continuous filaments of thermoplastic polymer. The nonwoven fabric as described in any one of 4.   The nonwoven fabric as described in any one of Claims 1-5 by which the extending | stretching process is not given. Randomly arranged, continuous thermoplastic filaments that form a strong spunbonded nonwoven fabric that is bonded together and bonded together at a plurality of bonding sites, and a plurality of formed by removing selected portions of the nonwoven web Consisting of apertures,
The spunbonded nonwoven fabric, wherein the plurality of apertures are configured to have an aperture ratio of at least 10% with respect to the surface area of the nonwoven fabric. A method for producing a perforated nonwoven fabric, comprising:
Guiding a nonwoven fabric composed of thermoplastic fibers into an embossing station along a predetermined traveling path, and passing the embossing station through the embossing station;
Contacting the nonwoven fabric with an embossing roll having a predetermined patterned surface at the embossing station;
The patterned surface applies heat and pressure to the nonwoven to thermally melt the thermoplastic fibers along a plurality of closed paths that define selected regions of the nonwoven surface, thereby An opening is formed in the selected region; and
Removing the selected region of the nonwoven from the remainder of the nonwoven.   The method of claim 8, wherein the selected region occupies at least 10% of the surface area of the nonwoven fabric.   The plurality of closed paths in which fibers are thermally melted constitute an embossed region, and the embossed region is configured to occupy 10% or less of the surface area of the nonwoven fabric, and the thermoplastic 9. A method according to claim 8, wherein the fiber surrounds a region of the nonwoven that is not melted and unembossed.   The method according to claim 10, wherein the plurality of closed paths in which the fibers are thermally melted have a surface area of 2% to 20% with respect to an area surrounded by the closed paths.   12. The method of any one of claims 8-11, wherein removing the selected area comprises directing air to the nonwoven to remove the selected area.   12. The method of any one of claims 8-11, wherein removing the selected area comprises contacting the nonwoven with a brush to remove the selected area.   14. The method according to any one of claims 8 to 13, wherein the applying heat and pressure comprises contacting the embossing roll with a heated anvil roll or ultrasonic anvil. An embossing roll for producing an apertured nonwoven fabric,
A cylindrical body, and a plurality of raised embossed portions located at predetermined locations separated from each other so as to cover the entire cylindrical surface of the cylindrical body,
The raised embossed portion comprises a raised land surface that contacts the nonwoven fabric extending along a closed path along the periphery of the raised embossed portion, and a concave surface surrounded by the raised land surface,
The embossing roll, wherein the raised land surface has a surface area of 2% to 20% with respect to an area surrounded by the raised land surface.   16. The raised embossed portion is provided on the roll at a density such that the raised land surface and the enclosed concave surface occupy at least 10% of the surface area of the cylindrical surface. Embossing roll.   The embossing roll according to claim 15 or 16, wherein the raised land surface occupies a surface area of 2% to 10% with respect to an area surrounded by the raised land surface.   The embossing roll according to any one of claims 15 to 17, wherein the raised land surface has a width of 10% to 30% with respect to a maximum width of the raised embossed portion.   The embossing roll according to any one of claims 15 to 18, wherein the raised embossed portion includes a circular shape or an elliptical shape.

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